The goal of this research is to understand how young children are able to function in complex acoustic environments, where multiple sources are often present. This includes identifying the location of sound sources, especially in noisy environments, and extracting the content meaningful sounds, such as understanding speech. This work will focus on children ages 4-7. We will measure binaural abilities using two paradigms. The first will evaluate children's ability to locate sounds, in quiet, in the presence of simulated echoes (precedence effect), and in the presence of "real world" competing sounds that are either spatially near or far from the target source. The second will focus on the children's ability to understand speech in the presence of competing speech and noise, and the extent to which they demonstrate a benefit from spatial separation of the speech and competing sounds (spatial release from masking). In adults, sound localization and spatial release from masking are known to be facilitated by the binaural system, however, surprisingly little is known about these abilities in young children. Previous work has shown that basic binaural processes are rudimentary at birth, and undergo many developmental changes during early childhood; however, the impact of these changes on children's abilities to cope with realistic complex environments remains to be understood. The long-term goal of this work is to extend our measures of auditory abilities to populations of children with sensori-neural hearing loss and with cognitive disabilities, including attention deficit disorders and autism.